1. Field of the Invention
In a broad aspect, the field of the invention is that of methods for provision of magnetized ferromagnetic components in an electrochemical apparatus wherein current-producing galvanic reactions are enhanced by means of the influence of magnetic fields established within the apparatus by the magnetized ferromagnetic components.
The present invention relates with special pertinence to battery electrodes which magnetically enhance the galvanic reaction in batteries energizing an external circuit in which current demand from an electrical load, such as a motor, tends to manifest discontinuities including high demand at unscheduled intervals.
The present inventor has been specifically engaged in investigation of internal battery structure modifications aimed at improved performance of battery-powered touring vehicles, such as the one testdriven by himself for the University of Victoria Electric Car Research Project, in British Columbia, the Canadian province with more mountain roads and wind than any other. The magnetized current collectors for batteries which he has devised have originated in response to the problem of transient decline in withdrawable current capacity of a battery, which is caused by discontinuous high electrical demands which arise, exascerbatingly, in circumstances inherently likely to occur when one attempts to tour, in a battery-powered vehicle, mountain roads of intermittently steep grade. Even when the road grade is flat, an electric vehicle's progress can be impeded by high headwinds. Highly variable external conditions in the service environment, in other words, translate into highly variable load demand, creating the ensuing capacity withdrawal limitation problem to which the present invention is chiefly directed.
The problem had in the past cast a shadow of doubt on the viability of lead-acid storage batteries for powering high performance road vehicles suitable for mountain touring.
Electrochemistry of the lead-acid storage battery entails that it has maximum capacity for discharge at constant low rate of current withdrawal. In this regard, and notwithstanding that the lead-acid battery is categorized a secondary battery, it is fairly representative of a wide variety of galvanic cells and batteries, both secondary and primary. In other words, there is no surprise that the suggested modification of the lead-acid battery which has recently been devised with the aim of minimizing impairment of electrode function in discontinuous high drain conditions should be found applicable to both primary and secondary cells and batteries--noting, however, that this is an eventuality which would not have been expected if the chief problem addressed by the inventor `this time around` concerned the electrolysis reaction involved in recharging of secondary batteries.
2. Description of Related Art
In practice, no real solid-state electrodes are atomically smooth, without asperities and/or a degree of porosity. Plate electrodes in lead-acid batteries are intentionally fabricated to have a degree of porosity providing electroactive surface areas several orders of magnitude larger than would be apparent from measurement of the plates' exterior planar dimensions.
Underutilization of the whole electroactive surface area, and an attending drop in withdrawable current capacity in high-load conditions, is associated with reduction of `penetration depth` into such plates to which needed ionic reactant entities can reach. Details of what happens are examined in a passage headed "ELECTROCHEMICAL KINETICS OF POROUS ELECTRODES", pages 151-159 in Lead-Acid Batteries, by H. Bode, (Wiley-Interscience, 1977).
An important early event in a too-high power demand condition is a kind of internal scavenging of reactant obtained not from the region of electrolyte between spaced-apart electrode plates but rather from electrolyte already internally present in pore networks. Consequent to this event, if the high load persists, is confinement of vital electron-transferring galvanic reactions to as little as only about half the number of possible reaction sites provided by the electrodes. While apparently regarding as impractical extra apparatus for solving this problem, Dr. Bode nonetheless acknowledges applicability of pumps to solving it, stating (last paragraph, p. 155):
"If a flow of electrolyte through the electrode is brought about by external forces, the diffusion-limited depth of penetration vanishes. Then, even on the high current loading, a capacity may be removed that approaches the maximum for long time discharges."
This statement reflects awareness of proposals for solving electrolyte transport difficulties by use of means such as the propellor, the rotating electrode, the gas bubbler, and the ultrasonic vibrator, which are depicted by Fig. 4.4 on page 130 of Electrochemical Science, J. O'M. Bockris and D. Drazic, (Barnes & Noble, 1972). More so than the other means, it seems, the ultrasonic vibrator has invited close comparison with use of magnetic means to stir electrolyte, to thin diffusion layers, to reduce electrical resistance, to minimize concentration over-potential, and even to promote smooth morphology of metal electrodeposited onto negative electrodes of electrolysis devices.
In a conclusory remark in their paper, "Electrothinning and Electrodeposition of Metals in Magnetic Fields", Journal of the Electrochemical Society, 119, pp. 51-56, (1972), J. Dash and W. W. King observe:
"Thus, if further research proves that magnetic fields are as effective as ultrasonic fields in improving electrodeposition and other important electrolytic processes, it would appear that the former have appreciable economic advantages."
A host of similarly directed observations may be retrieved from publications of workers in a subdivision of electrochemical research that has come to be called `magnetoelectrolysis`. Such research focusses on the effects of superposed magnetic fields upon electrolysis reactions in laboratory apparatus powered by current from some easily regulated source.
A sharp focus instead on magnetic field influence on galvanic reactions supplying current to a randomly variable external load would conceivably characterize a type of research for which the designation `magnetogalvanics` would be apt; however, because neither this term nor the focus thereby connoted seems yet to be retrievable from electrochemical research literature, findings in magnetoelectrolysis meanwhile provide useful background to the present invention. Reference is suggested to a review of magnetoelectrolysis issues provided by the present inventor, R. N. O'Brien, and a former colleague, K. S. V. Santhanam, in a passage entitled "MAGNETIC FIELD EFFECT ON ELECTRODEPOSITION", pages 453-464 in Techniques for Characterization of Electrodes and Electrochemical Processes, eds. R. Varma and J. R. Selman, (Wiley-Interscience, 1991). The present inventor's work making magnetoelectrolysis effects visually interpretable by means of laser interferometry have been cited in an overview article entitled "Applications of Magnetoelectrolysis", by R. A. Tacken and L. J. J. Janssen, Journal of Applied Electrochemistry., 25, 1 (1995).
Although there apparently have not been reports in journal literature which describe magnetic field effects on galvanic reactions, as distinct from effects on electrolysis, this lack is counterbalanced to some extent by descriptions appearing in two highly pertinent United States patents:
U.S. Pat. No. 3,597,278 (Aug. 3, 1971), ELECTROLYTIC CELL COMPRISING MEANS FOR CREATING A MAGNETIC FIELD WITHIN THE CELL, J. W. Von Brimer; and,
U.S. Pat. No. 5,051,157 (Sep. 24, 1991), SPACER FOR AN ELECTROCHEMICAL APPARATUS, R. N. O'Brien and K. S. V. Santhanam.
These are believed to constitute close prior art because both disclosures refer to use of permanent magnets integral with the construction of a modified lead-acid storage battery, and in both citations, at certain points, description of a magnetic field effect upon the galvanic reaction of a discharging battery is included.
With reference now to FIG. 4 of the VON BRIMER patent, when applied to a lead-acid battery the invention is described as preventing depletion during current delivery of sulfate ions between plates 12 and 14, in regions such as where magnetic flux lines 50 are shown in the figure. Substitution of an embodiment of the VON BRIMER invention in place of a pump for mechanical circulation of an electrolyte is mentioned at column 1, lines 54-68, and at column 4, lines 48-52, practicability of the invention in association with batteries other than the lead-acid type (chosen for illustrative purposes) is indicated. Concerning additional functions of the columns 32 of magnets 34--other than to serve as magnetic field generation means for establishing magnetic fields orthogonal to electrode plates--the function of substituting an assembly of such columns for plate spacing means receives some attention.
Indications of structure in the VON BRIMER disclosure which diverge in direction of teaching from below-described practice of the present invention include the insulation 52 coating the magnets 34, and their location centered between positive and negative electrode plates 12 and 14.
Next, the O'BRIEN ET AL disclosure shares a number of similar objects of invention with VON BRIMER. However, now referring to FIGS. 1 and 2 (O'BRIEN ET AL), the magnet-holding spacer 13, for central positioning between electrodes 11 and 12, has certain slits 17 which interact in a unique way with the "convective stream in the electrolyte" shown by arrows 20 in FIG. 2. Retrospectively, it appears that designing the slit angles to match the angle of "upwardly spiralling electrolyte" (col. 9, line 6) presupposes a known and reasonably low viscosity of circulated electrolyte. Assuming the sulfuric acid electrolyte to be used in the form of a dilute aqueous solution, viscosity data such as presented in Table 2.32 and Fig. 2.22 on pages 83 and 84 of the book by Dr. Bode cited above could be useful to a hypothetical artisan ordered to finalize design in detail of slits 17. The present inventor is uniquely placed to remark, however, that if an `immobilized` or gelled electrolyte had (contrary-to-fact) been suggested, such data could not be of help to the detailer of slits 17, who might reasonably be excused doubting compatibility of gelled electrolyte with the assigned task.
The present inventor perceives, albeit with hindsight, that in the VON BRIMER and O'BRIEN ET AL disclosures, a practicable range of electrolyte viscosity would have been desirable to specify, partly because of the emphases laid on circulation, and partly for reason of a recently surfaced suggestion or implication, from a new quarter, concerning relevance of stirrability.
New inventors on the scene have once again placed magnets in a battery--but this time indicate preference for using gelled electrolyte.
U.S. Pat. No. 5,728,482 (Mar. 17, 1998), SECONDARY BATTERY AND METHOD FOR MANUFACTURING THE SAME, S. Kawakami and N. Kobayashi, appears upon very close scrutiny to not anywhere describe a magnetic field effect specifically upon a galvanic reaction in a discharging battery. FIGS. 7 and 8 (KAWAKAMI ET AL) illustrate model experiments which manifest the inventors' understanding of the gist of their invention, which is directed to "disturbing the electric lines of force using a magnetic force" (column 6, lines 24-25) in order to promote uniform morphology of a metal (507 in FIG. 7; 508 in FIG. 8--same metal) electrodeposited onto negative electrodes 501 during a recharging process driven by current from external d. c. power source 503.
At column 6, line 64, the KAWAKAMI ET AL disclosure briefly refers to the "Lorentz force" to which Dash and King and other magnetoelectrolysis researchers have resorted in concerted attempts to account for observed uniformity of electrodeposition in magnetic fields--pertaining in the journal-reported research, however, to electrolyses using stirrable liquid electrolyte. Therefore it comes as a surprising new teaching to learn that magnetic field superposition enhances electrodeposition irrespective of electrolyte stirrabiliity. KAWAKAMI ET AL disclose the sufficiency of a solidified-state body supplying the plating metal, preference for gelation of the electrolyte being stated at column 12, lines 36-42.
Using liquid solution type electrolyte is retained as an option; and accordingly, there seems an implication that if the non-preferred liquid electrolyte were chosen, and convection is induced, then such convection could be a collateral effect with, and not the cause of, the observed morphology-smoothing effect on the metal.
It may be agreed that the `Lorentz force` which is considered effectual within certain limits to alter motion of matter is itself a result of interaction of an electric field and a magnetic field, which fields themselves are not phenomena requiring one or another particular state of matter in order to interact. In view of the uncertain nature of causal issues, an omission to mention convection is readily understandable as not wishing to trouble the hypothetical artisan building the battery with them.
Easier to grasp is an unexpected omission of mention in the KAWAKAMI ET AL disclosure of the lead-acid storage battery, some versions of which are known to employ gelled electrolyte, while many do not.
Lead-acid batteries typically have long service lives and are not especially prone to disablement by dendrites after only a few discharge/recharge cycles; thus, this prior art recharging technique (KAWAKAMI ET AL) is not needed with respect thereto.
To further distinguish KAWAKAMI ET AL, the present inventor refers to FIG. 2(a) and notes that the current-collecting porous nickel structure shown supporting both electroactive material and magnetic material is described at column 9, lines 45-46, without the slightest hint of suggestion that those magnetic grains 202 (and their weight) can be eliminated by magnetizing nickel collector 200.